Method of producing aqueous dispersions as a base for hot sealing adhesives

ABSTRACT

A hot-sealable coated substrate comprising a primer layer from an aqueous poly(meth)acrylate dispersion, comprised of: (A) 50-90 wt. % methacrylic acid esters; (B) 5-30 wt. % acrylic acid alkyl esters [lit., “acrylic acid acrylic esters”]; (C) 2-10 wt. % of another functionalized monomer; (D) 2-10 wt. % of a radically polymerizable carboxylic acid or a polycarboxylic acid or a partially esterified polycarboxylic acid; and (E) 0-40 wt. % of a monomer which is copolymerizable with components (A) to (D).

This application is a divisional application of U.S. application Ser.No. 09/033,607, filed Mar. 3, 1998 now U.S. Pat. No. 6,194,514 B1.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to aqueous dispersions based on poly(meth)acrylates, produced in a multi-state emulsion polymerization process,and to the use of such dispersions to prepare adhesives (bondingcompositions) which are susceptible to hot-sealing.

2. Description of the Background

In the past, hot-sealing compositions have been devised for thepackaging industry, which compositions fully meet the applicabletechnical criteria, but which contain substantial amounts of organicsolvents. E.g., Eur. Pat. 129,178 describes a hot-sealable coatingcomposition comprised of a film-forming dispersion of at least twodifferent polymer types with different adhesion properties in an organicsolvent system, wherewith the dispersion contains polymers of the twotypes and in addition contains a polymer comprised of unitscorresponding to the two polymer types. Vinylidene chloride polymershave also been used widely in the past as hot-sealable compositions.

Coating compositions for sealing metal substrates are of particularpractical and economic importance; in particular, compositions forproviding seals between aluminum and plastics such as polystyrene,polypropylene, and polyvinyl chloride, or between aluminum and glass.(See Ullmanns Enzyklopaedie der techn. Chemie, 6th Ed., 1985 ff., Vol16, pub. Verlag Chemie, pp. 101-103.)

Ger. Pat 4,209,651 (to BASF AG) describes an aqueous dispersioncontaining a copolymer A in the presence of which a polymerization iscarried out to produce a copolymer B. Copolymer A is produced by bulkpolymerization, and is not a core-and-shell product. The productmaterials are used in sealing PVC to paper board.

Jap. Pat. 08-231729 A (Derwent No. 96-461419/46). The products comprisecore-and-shell polymers produced by emulsion polymerization followed byspray drying. The shell has larger amounts of carboxyl-group-containingmonomers which improve the re-dispersibility of the product in water.

Rising awareness of environmental issues has created a trend away fromsolvent-containing formulations and toward aqueous dispersions such thatwhen, e.g., a coating or adhesive is applied to a surface, organiccompounds are not emitted into the environment. Also significant is thetrend away from chlorine-containing products, and, perhaps to a lesserextent, aromatic compounds.

Technology has been able to adjust, to some extent, to these morestringent requirements. Thus, as disclosed in Ger. 29 06 118, polymersof vinylidene chloride, used as hot sealing adhesives, may be applied inthe form of aqueous dispersions. In order to improve adhesion toun-primed plastic and metal sheets, special “anchoring agents” may beadded to the composition. Suitable such additives are water-solublepolymers of functionally substituted acrylamides and/or methacrylamides,or copolymers of these monomers with acrylamide and/or methacrylamide,which (co)polymers are present as species dissolved in the aqueous phaseof the dispersion.

Two methods of coating of aluminum foils and sheets are in widespreaduse:

In the case of relatively aggressive filler materials, first a primercoat of about 2 microns in thickness is applied to the aluminum foil.This primer is comprised of a vinyl-chloride-containing solutionpolymer. A finish coating comprised of a methacrylate resin of 4-8micron thickness is then provided over the primer coat.

For cases of less aggressive filler materials, a single-coat system isused, employing a hot-sealable coating of thickness of about 5-10microns comprising a mixture of the abovementioned polymers.

Still unsolved is the problem of providing a non-chlorinated,hot-sealing adhesive in the form of an aqueous dispersion with adequateadhesion. Ger. 27 27 914 (U.S. Pat. No. 4,291,090) and Ger. 28 55 147disclose hot-sealing adhesives based on polyacrylate which can beapplied as aqueous dispersions. In some cases, these adhesives are notcomprised exclusively of esters of (meth)acrylic acid. That is, they maycontain one or more comonomers, employed, e.g., for the purpose ofmodifying the melting temperature, hardness, or adhesion properties ofthe adhesive. Suitable comonomers include, inter alia, (meth)acrylamide,and aminoalkyl esters of acrylic acid and/or of methacrylic acid. Thespecific effects which these comonomers have on the properties of thepolymers is not disclosed.

Ger. 39 30 743 (Can. Pat. App. 2,025,368.1) describes an aqueouspolyacrylate dispersion, which is useful as a hot-sealing adhesive,based on at least 70 wt. % of a polyacrylate comprised of units of loweralkyl methacrylates and also containing polymerized (meth)acrylamide oraminoalkyl (meth)acrylate. Other publications relate to aqueousdispersions of copolymers of olefins and/or vinyl acetate, whichcopolymers contain units of chlorinated monomers and are produced in asingle-stage process. The described dispersions exhibit poor adhesion toaluminum substrates.

Polymer dispersions, which are prepared from polymer particles having acore-and-shell structure, which are described in the literature, eithercontain chlorinated monomers or are not suitable for bonding plastics toaluminum.

Eur. Pat. 574,803 describes aqueous polymer dispersions of 5-80 wt. % ofa copolymer (A), having a glass transition temperature of 50-150° C.,and 95-20 wt. % of a copolymer (B), having a glass transitiontemperature of −50 to +50° C., the two copolymers in the compositionhavingwith a temperature difference of 20° C. There is no specificindication in this publication that the proposed products are suitablefor bonding plastics to aluminum.

Further, no appropriate two-coat methods are described in the citedstate of the art references.

A two-coat coating is proposed in Jap. Pat. App. 54-161,684 (Chem.Abstr.92:199427x). First, an aluminum foil is coated with the aqueousdispersion of a monomer and then with a mixture of an ethylene-vinylacetate copolymer, colophony, and wax, to a thickness of 20 microns.

In connection with the object of formulating chlorine-free aqueouspolymer dispersions for use as hot-sealing adhesives, another problemexists which is the problem of compatibility with the state of the artapparatus employed. This problem is particularly significant in thelarge-scale coating of aluminum foils and sheets. In particular, oneshould be able to use customary methods of applying polymers as thinfilms (see Polymer Handbook, 2nd Ed., pub. Hanser Verlag), and the filmsemployed should not be sticky at ordinary temperatures.

A requirement imposed on means of hot sealing an adhesive to a suitablesubstrate is that good adhesion for bonding the two materials (e.g.aluminum and polystyrene) must be achieved in a short time and attemperatures which are not excessive and which are about, e.g., 180-220°C.

The proposed packaging methods are also intended for used withfoodstuffs. In such applications, the monomers and the adjuvants must beselected such that the regulations governing food packaging (GermanFederal Health Office guidelines BGA 14, and the corresponding US FDAguidelines) are complied with.

In Ger. 39 30 743 an aqueous dispersion is proposed which has adequateadhesion to an aluminum foil substrate coated with a vinyl chloridecopolymer as a primer. Efforts to modify such dispersions byincorporating units of adhesion-promoting monomers in order to provide avariant which can be applied to un-primed aluminum have not beensuccessful. Thus the reference does not provide a solution to theproblem of replacing chlorinated primers. Other efforts using similarapproaches, using polymers with simple particle structures, have notbeen successful.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide anaqueous polymer dispersion of improved hot-sealing and adhesioncharacteristics to plastic and metal substrates.

Another object of the present invention is to provide aqueous poly(meth)acrylate dispersions PD. which are produced by emulsion polymerizationand which have at least a two-stage particle structure, for use ashot-sealing adhesives.

Briefly, these objects and other objects of the present invention ashereinafter will become more readily apparent can be attained by aqueouspoly(meth)acrylate dispersions, comprising:

a particulate poly(meth)acrylate comprising the following components:

(A) 50-90 wt. % of methacrylic acid alkyl esters;

(B) 5-30 wt. % of an acrylic acid alkyl ester having a glass transitiontemperature Tg in the range c. −20 to 50° C. and having formula I:

 wherein R₁ represents an alkyl, aryl, or alkaryl group having 2-10 Catoms;

(C) 2-10 wt. % of a functionalized monomer of formula II:

 wherein R₂ represents hydrogen or methyl; and R₃ represents a glycidylgroup

 or an alkyl group which has 2-6 C atoms and is substituted with atleast one hydroxyl group;

(D) 2-10 wt. % of at least one radically polymerizable carboxylic acidor a polycarboxylic acid or a partially esterified polycarboxylic acid;and

(E) 0-40 wt. % of other monomers which are copolymerizable with (A) to(D);

wherewith, in the process of preparation, a first polymerization stage(Process Step 1) is conducted with monomers of groups (A) to (C) andoptionally (E), and in a second polymerization stage (Process Step 2),monomers of groups (A), (B), (D), and optionally (E) are copolymerized;and wherewith the sum of the amounts of monomers (A) to (E) is 100 wt.%.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The sum of the percentages of monomer units from groups (A) to (E) is100 wt. %. The preferred monomer of formula I is n-butyl acrylate.Preferred monomers of formula II include glycidyl (meth)acrylate andhydroxyethyl (meth)acrylate.

Suitable monomers for group (E) monomers include styrene, (C₁ toC₄)-alkylstyrene compounds, cycloalkyl (meth)acrylates, and the like.Data on glass transition temperatures TG may be found in, e.g., Kirk andOthmer, 1978, “Encyclopedia of Chemical Technology”, 3rd Ed., pub. J.Wiley, Vol. 1, pp. 387-389.

The ratio of the materials in the first polymerization stage to themasterials in the second polymerization stage ranges from 30:70 to 70:30parts by weight (pbw). A recommended rule for the proportioning of thepolymerization stages is that the amounts should not differ by more thana factor of 2.5.

Additional preferred embodiments of the reaction include the following:

(i) The methacrylate content of the monomers polymerized in the firststage should be about 60±20 wt. %.

(ii) The content of monomers of formula I in the monomers polymerized inthe first stage should be about 30±10 wt. %.

(iii) The content of monomers of fonnula II in the monomers polymerizedin the first stage should be about 10±5 wt. %.

(iv) The remainder of the monomers to complete 100 wt. % of the monomersin the first stage is the monomer of group (E).

Still further preferences include:

(i) The content of methyl methacrylate and/or monomers of group (E) inthe monomers polymerized in the second stage should be c. 20±10 wt. %.

(ii) The content of (meth)acrylic acid in the monomers polymerized inthe second stage should be about 12±8 wt. %.

For each stage of polymerization, the sum of the percentages of all themonomers is 100 wt. %.

The molecular weights of the poly(meth)acrylates in the dispersion PDare generally in the range>20,000 g/mol. The polymer content of thedispersions is generally in the range 20-65 wt. %; and the particlesizes are generally in the range 60-250 nm, preferably 80-160 nm,particularly preferably 100-40 nm (determined by photon correlationspectroscopy).

The poly(meth)acrylate dispersion PD of the invention is produced byemulsion polymerization in the aqueous phase in the presence of anionic,cationic, or nonionic emulsifiers, which emulsifiers are per se known,and in the presence of at least one radical-forming initiator, in atwo-stage reaction (see Rauch-Puntigam, H., and Voelker, Th., 1967,“Acryl- und Methacrylverbindungen”, pub. Springer-Verlag, pp. 217-230).

It should be noted that certain advantageous properties, e.g. resistanceto peeling, as specified in food packaging regulations (BGA 14guidelines, and the corresponding US FDA guidelines), can be achievedwith the use of additives.

The first stage may be conducted as a controlled-feed process: Asuitable reaction vessel equipped with a stirrer and heater is initiallycharged with deionized water and emulsifier(s). Subsequently, after acertain temperature is reached, the initiator, preferably dissolved inwater, is added. The initiator may be, e.g., an inorganic peroxide suchas potassium peroxydisulfate (KPS) or ammonium peroxydisulfate (APS). Itis recommended that the content of initiator in the mixture at thispoint be in the neighborhood of 0.8 wt. %, based on the weight of themonomers reacted in Process Step 1.

Suitable ionic emulsifiers, which are used in amounts of 0.01-2.0 wt. %,based on the total weight of monomers, include anionic emulsifiers suchas Aerosol OT75(R) of Cyanamid BV and “Dowfax 2A1” of Dow Europa SA.

The addition of the above-described mixture for Process Step 1 is acontrolled feed over a prescribed period of time, e.g. 2 hr, in thefirst stage. As an example, the feed mixture for Process Step 1 maycomprise 20-60 wt. % of the total water to be used, plus the monomers ofgroups (A) to (C) and optionally (E).

Advantageously, the mixture is then mixed for an additional period oftime, e.g. 1 hr, at elevated temperature, e.g. 80° C., following whichit is allowed to cool, e.g. to 30° C. The monomers described above inconnection with “Process Step 2” are then added dropwise over arelatively short period of time, e.g. 30 min, and the mixture is thenallowed to stand for an appreciable period of time, e.g. 4 hr.

The resulting aqueous monomer/polymer mixture is then heated slightly,e.g. to 40° C., and additional radical initiator, preferably aredox-type initiator, e.g. comprised of peroxydisulfate. dithionite, andiron(II) sulfate, is added in water. and further polymerization isinitiated.

After the maximum temperature is reached. advantageously the temperatureis controlled, e.g. at 80° C., and the mixture is stirred for anadditional period, e.g. 2 hr, to complete the polymerization.

Alternatively, the second stage can be carried out as anothercontrolled-feed “semicontinuous” step, with addition of a monomeremulsion gradually over a period of, e.g., 2 hr.

The mixture is cooled to about 30° C., and advantageously a suitablepreservative is added, e.g. Acticid SPX(R) of Thor Chemie GmbH. alongwith a small amount of ammonia (as 25% ammonia in water).

One may also add 0-5% of nonionic emulsifiers, e.g. ethoxylatedalcohols, or methacrylate esters of methoxypolyethylene glycols, e.g.“Carbowax 550”, or alkylphenols, and also an additional amount of ananionic emulsifier.

As a rule, the polymer dispersion (PD) may be used directly for coating.In certain cases limited amounts of thickeners or film-forming agentsmay be employed. The coating may be applied by spraying, brushing,pouring, dipping, blade-coating, or roll-coating. Generally the coatingis applied in a thickness such that the dried coating has a thicknesssuch that the dried coating layer is 2-10 microns thick.

Advantageously, the coated articles are dried in a drying oven or bycontinuously conveying the coated articles through a drying tunnel,possibly at reduced pressure and at temperatures in the range 100-200°C.

In general, the higher the drying temperature, the shorter the dryingtime. Drying times are, e.g., in the range 5 sec to 5 min. It ispossible to apply the coating in multiple coats. Preferably, thesubstrate to which the polymer dispersion (PD) is applied has anon-porous and continuous (“closed”) surface, e.g. the surface of aplastic film or sheet. or particularly of a metal foil or sheet, e.g.aluminum foil or iron.

As stated above. one advantage of using the present poly(meth)acrylatedispersions (PD) as hot-sealing adhesives is that they solve theimportant and urgent problem of formulating a hot-sealable compositionbased on an aqueous acrylate dispersion, e.g. the type of dispersiondisclosed in Ger. 39 30 74, which composition adheres strongly tosubstrates, particularly metal foils or sheets, and in particularaluminum foils or sheets.

Accordingly, the principal embodiment of the present invention ishot-sealable coated substrates, particularly of metal or plastic, coatedwith the present poly(meth)acrylate dispersion(s) (PD) as a primerlayer, with a second layer applied over the primer layer comprised of anaqueous poly(meth)acrylate dispersion comprised of:

at least 70 wt. % of at least one C₁C₄-alkyl ester of (meth)acrylicacid; and

an appreciable amount of (meth)acrylamide and/or aminoalkyl(meth)acrylate;

wherewith the second laver is applied over the dried primer layer, andthen dried.

For details beyond those provided in the example embodiments describedbelow reference is made to the disclosure of Ger. 39 30 743. Arepresentative such dispersion and the means of its application aredescribed hereinbelow (see Part II of the Example section).

In hot-sealing, the temperature in the coating must exceed the glasstransition temperature of the poly(meth) acrylate. The temperature ofthe hot contact members which effect the sealing must exceed therequired sealing temperature by an amount which increases as the contacttime is decreased and as the heat conduction through the substrate layeris decreased. A thin metal foil has very good heat conduction, enablingthe hot contact members to be at a temperature which is only slightlyabove the melting temperature of the poly(meth)acrylate. However, inpractice the fastest possible sealing is desired, necessitatingsubstantially higher temperatures of the hot contact members, e.g.120-220° C. In the case of a plastic substrate, the hot contact membertemperature may have to be limited because of the glass transitiontemperature of the plastic. To obtain a seal of high strength, thepressure exerted by the hot contact members should be at least 1 kp/cm²,preferably 3-6 kp/cm².

The effective peeling resistance of hot-sealing samples from theExamples was tested in the customary fashion (sealing seam strengthaccording to DIN 51 221).

The objective was to demonstrate that, e.g., the use of the presentpoly(meth)acrylate dispersions as primers on aluminum foils or sheets,along with the use of the aqueous dispersions of Ger. 39 30 743, as anouter hot-sealable layer provides adhesive properties equivalent tothose provided with primers based on solvent-containing and/orchlorinated polymers.

Having now generally described the invention, a further understandingcan be obtained by reference to certain specific examples which areprovided herein for purpose of illustration only and are not intended tobe limiting unless otherwise specified.

The production and testing of hot-sealed samples is describedhereinbelow, and a table of the strengths of the seals is be presented.

COMPARATIVE EXAMPLES

To produce the comparative samples, a 10 wt. % solution of a commercialvinyl chloride/ vinyl acetate/ maleic acid copolymer (“Vinylite VMHC”,supplied by Union Carbide) in ethyl acetate was applied with a spiralblade applicator to a 40 micron thick soft aluminum foil, in a thicknesssuch that after drying 1 min at 180° C., a primer of thickness 2 micronwas produced. The present poly(meth)acrylate dispersions (PD) wereapplied with a blade applicator, and, to form a film, were immediatelyplaced in a circulating air drying cabinet preheated to 180° C. beforethe water had evaporated from the dispersion coating. The applicator wasselected such that the layer of dried hot-sealable adhesive hadthickness of 0.5-3.0 micron.

The poly(meth)acrylate dispersions of Ger. 39 30 743 can be applied by asimilar technique, after drying of the poly(meth)acrylate dispersions(PD).

The coated aluminum foils were sealed to polystyrene films and PVCfilms, respectively, on edge regions 1 cm wide, using a laboratory-scalehot sealing apparatus (manufactured by Brugger). The temperature of thehot contact members was 180° C., the sealing pressure was 6 kp/cm², andthe sealing time was 1 sec.

Seal strength was measured by the procedure described in DIN 51 221. Thesamples were first stored in a standard atmosphere (23° C., 50% relativehumidity). Strips 15 mm wide were cut transversely to the seal seam,folded outward, and tested in a tensile testing machine, with one of theholding clamps gripping the free end of the aluminum foil and the othergripping the free end of the plastic film, wherewith the tensile forcewas exerted approximately transversely to the sealing seam on the teststrip. The seal seam strength was taken to be the force required toadvance the separation of the foil and film to the extent of 15 mm.

To test water resistance of the seal seam, the sample strips were stored48 hr in water at room temperature, then tested for seal strength in thewet state by the above-described method.

EXAMPLES 1-20 (TABLE 1) Ia. General Method of ProducingPoly(meth)acrylate Dispersions PD with Emulsion Polymerization

Process variants:

(Iaa) Controlled feed (“semicontinuous”) process.

(Iab) Controlled feed followed by batch.

(Iac) Controlled feed followed by controlled feed.

Into a round-bottom flask equipped with a stirrer, contact thermometer,and heater, were charged deionized water and an emulsifier (AerosolOT75(R)), and heating was begun. After the temperature reached 90° C.,ammonium peroxydisulfate (APS) dissolved in water was added as aninitiator, and Process Step 1 was begun.

(Iaa) For variant Iaa, the feed was added gradually over 240 min,followed by stirring at 80° C. for an additional 2 hr, to allowcompletion of the polymerization.

(Iab) For variant lab, the feed for Process Step 1 was added graduallyover 120 min, followed by stirring at 80° C. for an additional 1 hr, andcooling at 30° C. Then the feed for Process Step 2 was added dropwiseover 30 min, following which the mixture was allowed to stand 4 hr. Themonomer/polymer mixture was then heated to 40° C. and a redox initiatorwas added. After the maximum temperature was reached, the temperaturewas maintained at 80° C. and stirring was continued for an additional 2hr, to allow completion of the polymerization.

(Iac) For variant Iac, the feed for Process Step 1 was added graduallyover 120 min, followed by stirring at 80° C. for an additional 40 min.Then the feed for Process Step 2 was added gradually over 2 hr,following which the mixture was stirred for an additional 2 hr to allowcompletion of the polymerization.

In all three variants (Iaa) to (Iac), a preservative in water was thenadded (for amounts, see Table 3).

The data for Examples 1-19 are presented in Tables 1 and 3. Table 1gives the monomer compositions, amounts of emulsifier, and amounts ofwater, for Process Step 1 and Process Step 2. Table 3 gives the amountsof various additives.

Ib. Production of the Poly(meth)acrylate Dispersions by EmulsionEpolymerization in a Process Comprising a Batch Process Followed by aControlled Feed Process

Into a round-bottom flask equipped with a stirrer, contact thermometer,and heater were charged the materials for the batch preparation (ProcessStep 1). The monomer mixture was the heated to 40° C. and a redox-typeinitiator was added, to initiate the polymerization. After the maximumtemperature was reached, the temperature was maintained at 80° C. andstirring was continued for an additional 40 min. Then the feed for thecontrolled feed process (Process Step 2) was added gradually over aperiod of 2 hr. following which the mixture was stirred for anadditional 1 hr to allow completion of the polymerization. Thepreservative was then added at 30° C.

For example 20, Table 1 gives the monomer compositions, amounts ofemulsifier, and amounts of water, for Process Step 1 and Process Step 2,and Table 3 gives the amounts of various additives.

II. Production of an Aqueous Polyacrylate Dispersion (according to Ger.39 30 743, “Coating for use as a Sealant”)

In a 1-liter round-bottom flask equipped with a stirrer, contactthermometer, and heater, 60 pbw of fully desalinated water and 0.05 pbwof sodium diisooctylsulfosuccinate were heated to 80° C. with stirring,and 2.4 pbw of a 10 wt. % solution of ammonium peroxydisulfate (APS) wasadded. Thereafter, the following were added dropwise over a period of 4hr, also at 80° C.;

(i) An emulsion comprised of 240 pbw completely desalinated water, 4 pbwsodium diisooctyl sulfosuccinate, 1 pbw APS, 320 pbw butyl methacrylate,72 pbw methyl methacrylate, and 8 pbw methacrylic acid amide, along with

(ii) A regulator comprising 0.4 g dodecyl mercaptan. After another 2 hrat 80° C., the mixture was cooled to room temperature. A stablecoagulate-free dispersion was obtained. The solids content was about 50wt. %. Mean particle diameter was 340 nm. The viscosity was 40 mPa-sec,as determined with a Brookfield viscosimeter.

III. Testing of the Hot Sealing Properties

For examples 1-20 (with Examples 1-3 being comparative examples), acoating 1.5 micron thick comprised of the respective poly(meth)acrylatedispersion (PD) was applied to an untreated aluminum foil, followed bydrying 1 min at 180° C. Then a coating 7 micron thick comprised of thedispersion of Sec. II was applied, again followed by drying 1 min at180° C. Strips 15 mm wide comprised of the thus treated aluminum foilswere sealed against a polystyrene film. Sealing duration was 1 sec, withthe hot contact members being at 180° C. and exerting a pressure of 6kp/cm².

The adhesive strengths of these bonded structures are given in Table 4.If the bond failed a hand separation test, the measurement was notperformed. The first value of resistance to peeling given is the valuefor the dry bond; the second is the value after storing 48 hr in water.

Results:

The results demonstrate that by a rational selection of the monomers andthe production process, aqueous polymer dispersions of the invention canbe produced which yield primer layers on aluminum foil which primersprovide adhesive properties equivalent to those provided with primersbased on solvent-containing and/or chlorinated polymers.

IV. Testing of Adhesion of Primers to Various Metallic Substrates

A variety of metal plates (“BM”) comprised of aluminum or iron werecleaned with ethyl acetate. The dispersion being tested was applied tothe desired site by means of a film drawing apparatus, with gap heightsof 20 micron, 80 micron, and 100 micron. Also, dispersions to which 4%butyldiethylene glycol acetate (“BDGA”) had been added were applied,using gap heights of 100 micron and 200 micron. The adhesion wasmeasured by a grid-cutting test (with an a added Tesa film-peelingtest), evaluated visually.

Results:

In all instances, the films adhered well.

Table 1 (parts 1 and 2 of 2):

Dispersions (PD) prepared according to variant methods Iaa, Iab, Iac,and Ib:

[For Table 1 parts 1 and 2, see 2 pages following the text.]

KEY to Table 1:

Columns:

(a) Process;

Examples 1-3. (comparison examples). [Method variant] Iaa;

Examples 4-17. [Method variant] lab, first process step is controlledfeed process, second process step is batch;

Examples 18-19. [Method variant] lab, first process step is controlledfeed process, and second process step is controlled feed process.

Examples 20. [Method variant] Ib [lit., “Iab”], first process step isbatch, and second process step is controlled feed process.

Rows:

(b) First process step (controlled feed for Examples 1-19; batch forExample 20).

(c) VINYLITE VMHC=Vinyl Chloride/Vinvl Acetate/Maleic Acid Copolymer(supplied by Union Carbide), dissolved in ethyl acetate.

Iaa Iaa Iaa Iab Iab Iab Iab Iab Iab Iab Ex- Process Example 1 Example 2Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9ample 10 First Semicon- Semicon- Semicon- Semicon- Semicon- Semicon-Semicon- Semicon- Semicon- Semicon- Step tinuous tinuous tinuous tinuoustinuous tinuous tinuous tinuous tinuous tinuous Water 533.7 531 531509.7 509.7 510.6 509.7 509.7 509.7 509.7 Aerosol 8.5 8.55 8.55 8.558.55 8.55 8.55 8.55 8.55 8.55 OT75(R) Methyl 39.5 360 270 270 270 292.5281.25 292.5 270 Methacrylate Butyl Acrylate 35 135 135 135 135 135 135135 135 135 Glycidyl 45 Methacrylate Hydroxyethyl 45 45 45 45 22.5 33.7522.5 45 Acrylate Butyl 697.5 Methacrylate Methacrylamide 18 Methacrylic22.5 Acid Acrylic Acid 22.5 45 45 Butyl 315 315 Methacrylate Styrene 360Dodecyl 0.45 Mercaptan Second Step Example Example Example ExampleExample Example Example Butyl 315 315 315 315 315 315 315 MethacrylateMethyl 90 90 112.5 101.25 90 112.5 Methacrylate Acrylic Acid 45 45 4522.5 33.75 45 22.5 Styrene 90 Polycarboxylic Acid* Aerosol OT75(R) WaterAmmonium Peroxydisulfate (Continued) Dispersions PD Prepared Accordingto Variant Methods Iaa, Iab, Iac, and Ib: Iab Iab Iab Iab Iab Iab IabIab Iab Ib Example Example Example Example Example Example ExampleExample Example Example Process 11 12 13 14 15 16 17 18 19 20 FirstSemicon- Semicon- Semicon- Semicon- Semicon- Semicon- Semicon- Semicon-Semicon- Semicon- Step tinuous tinuous tinuous tinuous tinuous tinuoustinuous tinuous tinuous tinuous Water 482.2 482.2 482.2 482.2 814.3482.2 370.4 266.9 361.5 629.2 Aerosol 8.55 8.55 8.55 8.55 3.43 8.55 10.34.28 3 0.9 Methyl 270 270 270 270 198 270 324 270 270 270 MethacrylateButyl Acrylate 135 135 135 135 54 135 162 135 135 135 GlycidylMethacrylate Hydroxyethyl 45 45 45 45 18 45 54 45 45 45 Acrylate ButylMethacrylate Methacrylamide Methacrylic Acid Acrylic Acid ButylMethacrylate Styrene Dodecyl Mercaptan Semicon- Semicon- Semicon- SecondStep Example Example Example Example Example Example Example tinuoustinuous tinuous Butyl 315 315 315 315 126 315 378 315 315 315Methacrylate Methyl 90 90 36 90 108 90 Methacrylate Acrylic Acid 45 4545 45 18 54 45 45 45 Styrene 90 90 90 90 Polycarboxylic 12.5 Acid*Aerosol 4.28 3 788 Water 266.9 261.5 2104 Ammonium 0.9 0.9 0.9Peroxydisulfate *Polycarboxylic Acid-Rohagit SL 140

TABLE 2 Amounts of Additives Second Process Step (but first process stepin Example 20) Initial Charge to Reactor Sodium After PolymerizationAerosol Ammonium Ammonium Hydroxymethyl Acticid SPX Example WaterOT75(R) Peroxydisulfate^(a) Peroxydisulfate^(a) Fe₂(SO₄)₃ ^(b) Na₂S₂O₅^(c) Sulfinate^(d) in 10 g water NH₃ ^(e) 1 340 0.255 2.7 1.8 0.34 2 3400.225 2.7 1.8 0.34 3 340 0.225 2.7 1.8 0.34 4 346 0.225 2.7 0.72 0.00090.36 1.8 0.34 5 340 0.225 2.7 0.72 0.0009 0.36 1.8 0.34 6 340 0.225 2.70.72 0.0009 0.36 1.8 0.34 7 340 0.225 2.7 0.72 0.0009 0.36 1.8 0.34 8340 0.225 2.7 0.72 0.0009 0.36 1.8 0.34 9 340 0.225 2.7 0.72 0.0009 0.361.8 0.34 10 340 0.225 2.7 0.72 0.0009 0.36 1.8 0.34 11 340 0.045 2.70.72 0.009 0.504 1.8 0.34 12 340 1.8 2.7 0.72 0.009 0.504 1.8 0.34 13340 0.045 2.7 0.72 0.009 0.504 1.8 0.34 14 340 1.8 2.7 0.72 0.009 0.5041.8 0.34 15 556 0.091 1.08 0.288 0.0043 0.202 0.72 0.135 16 340 0.2252.7 0.72 0.009 0.504 1.8 0.34 17 268 0.27 3.24 0.864 0.011 0.605 2.160.41 18 340 0.225 2.7 1.8 0.34 19 340 0.3 0.9 1.8 0.34 20 0.72 0.0090.504 1.8 0.34 ^(a)Ammonium Peroxydisulfate dissolved in 20 g water^(b)Fe₂(SO₄)₃ dissolved in 10 g water ^(c)Na₂S₂O₅ dissolved in 20 gwater ^(d)Sodium Hydroxymethyl Sulfinate dissolved in 20 g water ^(c)20%Ammonia in 5 g water

TABLE 4 Measurements of resistance to peeling Peeling Strength, N, for15 mm strip width: Seal between aluminum and Seal between polystyrene(“PS”) aluminum and PVC Example After 48 hr After 48 hr Number Normalpressed in water Normal Pressed in water 1 Value too low 2 4.8 1.7 2.11.1 3 5.7 3.7 3.1 1.7 4 6.9 8.0 6.7 5.8 5 8.1 4.3 5.1 2.5 6 7.0 6.0 3.82.4 7 Value too low 8 Value too low 9 Value too low 10 Value too low 116.9 4.7 3.4 2.9 12 5.0 6.2 3.3 3.3 13 4.7 2.3 2.3 2.3 14 7.6 7.4 4.8 3.715 4.2 6.8 1.9 2.4 16 4.2 4.9 1.9 2.1 17 5.9 1.9 3.9 2.9 18 2.0 0.6 1.30.7 19 8.1 8.0 6.9 5.6 20 3.8 4.3 2.4 2.6

TABLE 5 Results of adhesion tests of Example 9 sample, usinggrid-cutting test. (Data are the number of fields loosened in the test.)Film according to Example 19 + 4% butyldiethylene glycol acetate(“BDGA”), applied to solid metal plates (“BM”) Drying 180° C., 2 Drying180° C., 1 minutes Film according to Example 19 minutes; applicationapplication with Drying 180° C., 1 minute; Drying 180° C.,2 minutes;with film-drawing film-drawing application with film-drawing applicationwith film-drawing apparatus; column apparatus; column apparatus; columnheadings are apparatus; column headings are headings are gap headingsare gap gap height (micron) gap height (micron) height (micron) height(micron) 20 μm 60 μm 100 μm 20 μm 60 μm 100 μm 100 μm 200 μm 100 μm 200μ Actual coating thickness 12-19 14-28 15-27 14-18 13-17 12-33 15-2833-46 20-30 −40 (micron)(measured on the Fe plate) Iron plate 0/0 0/00/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 Aluminum plate 2/4)*** 0/0 0/0 0/0 0/00/0 0/0 0/0 0/0 0/0 ***Drying was not optimal for this [failing] test.

German priority application 197 08 412.5 filed Mar. 3, 1997 is herebyincorporated by reference into the present application.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. A hot-sealable coated substrate prepared by aprocess, comprising: applying a first aqueous poly(meth)acrylatedispersion to a substrate comprising metal or plastic as a primer layer;drying said primer layer, thereby providing a dried primer layer;applying a second layer on said dried primer layer; and drying saidsecond layer; wherein said first aqueous poly(meth)acrylate dispersioncomprises: a particulate poly(meth)acrylate comprising the followingcomponents: (A) 50-90 wt. % of a methacrylic acid alkyl ester; (B) 5-30wt. % of an acrylic acid alkyl ester having a glass transitiontemperature Tg in the range of −20 to 50° C. and having formula I:

 wherein R₁ represents an alkyl, aryl, or alkaryl group having 2-10 Catoms; (C) 2-10 wt. % of a functionalized monomer of formula II:

 wherein R₂ represents hydrogen or methyl; and R₃ represents a glycidylgroup of the formula

 or an alkyl group which has 2-6 C atoms and is substituted with atleast one hydroxyl group; (D) 2-10 wt. % of at least one radicallypolymerizable carboxylic acid or a polycarboxylic acid or a partiallyesterified polycarboxylic acid; and (E) 0-40 wt. % of other monomerswhich are copolymerizable with (A) to (D); wherein, in the process ofpreparation, in a first polymerization stage monomers (A), to (C) andoptionally (E) are copolymerized; wherein in a second polymerzationstage monomers (A), (B), (D) and optionally (E) are copolymerized; andwherein the sum of the amounts of monomers (A) to (E) is 100 wt. %. ineach polymerization stage; and wherein said second layer comprises asecond aqueous poly(meth)acrylate dispersion; comprising: (i) at least70 wt. % of at least one C₁-C₄-alkyl ester of methacrylic acid; and (ii)a compound selected from the group consisting of an acrylamide, amethacrylamide, an aminoalkyl acrylate, an aminoalkyl methacrylate or acombination thereof.
 2. The substrate of claim 1, wherein a content ofmonomers polymerized in said first polymerization stage is 60±20 wt. %based on a total amount of monomers (A) to (C) and (E); wherein saidmethacrylate comprises methacrylic acid alkyl ester, glycidylmethacrylate and optionally a methacrylate copolymerizable with monomers(A) to (C).
 3. The substrate of claim 1, wherein a content of saidmonomer of formula I in said monomers polymerized in said firstpolymerization stage is 30±10 wt. % based on a total amount of monomers(A) to (C) and (E).
 4. The substrate of claim 1, wherein a content ofsaid monomer of formula II in said monomers polymerized in said firstpolymerization stage is about 10±5 wt. % based on a total amount ofmonomers (A) to (C) and (E).